This invention generally relates to devices used to regulate the pressure of a fluid supply and more specifically to the design of a pressure regulator valve capable of providing a duplex of fluid sources with a substantially constant differential pressure regardless of the fluctuation in pressure of multiple fluid supplies.
Most general aviation aircraft utilize gyroscopic instruments as the primarily flight control inputs for flying without reference to the horizon. These instruments are driven either by differential air pressure or electricity. In order to provide the maximum redundancy, especially in an aircraft with a single reciprocating engine, some of these instruments are driven by electricity and some by differential pressure. The vacuum supply (or positive pressure in some cases) is typically a vane-type pump driven by the engine. These pumps, operating at approximately 5 inches mercury differential pressure, are considered to be among the least reliable devices on the aircraft. There have been a number of improvements proposed to reduce the dependency on the pump or to provide a back-up system. Some aircraft utilize 2 pumps driven by the same engine for redundancy, sometimes with a clutch driving one in order to reduce wear on the back-up pump. Another method is to provide an electric motor-driven back-up pump, but this is heavy and expensive and significantly increases the electrical load when the primary vacuum pump fails. A low cost solution has been to use the natural vacuum that exists in the intake manifold of a reciprocating engine for the source. This, and many of the other devices, must use a manual valve to activate the stand-by source, increasing the pilot workload. When using the intake manifold as a source that vacuum is only available at partial engine load, forcing the operator to reduce the engine power to supply air to the instruments. Also, this approach is not effective with supercharged engines which are being used in increasing numbers in light aircraft, because the manifold pressure is above atmospheric in most operating conditions.
In one of a number of possible applications, a pressure regulator valve described by the present invention can effectively utilize pressure in the intake manifold of a turbocharged engine to provide a supply differential pressure. Moreover, it is able to provide this differential pressure source at all normally used power settings. There are two pressure taps taken from the engine, one at the compressor (supercharger) outlet and the other at the intake manifold downstream of the throttle valve. Additional pressure ports are vented to atmospheric pressure. The device will automatically utilize the highest pressure available for the instrument source and the lowest available pressure for the discharge with priority given to operation with the upstream side vented to atmosphere and the downstream side at a relative depression. This system operates with such reliability that a redundant or back-up system is unnecessary.
This invention combines common components (diaphragms, springs, disc valves, etc.) in such a way as to perform a function not possible with conventional technology. This function is the supply of a differential pressure source that is adequate--in this case to power flight instruments--when neither the high pressure source or the low pressure source are always adequate for the task.
The advantages of the present invention when used to replace existing technology instrument drive systems for light aircraft include lower cost, lower weight and greater reliability.